This invention relates generally to ferrocyanide type conversion solutions, and, more particularly, to compositions containing organic amine additives for solvating salt crystals which form in such solutions during usage.
The use of conversion solutions of the type using a ferrocyanide is well known in the art. Improvements have been made in the composition of such conversion solutions, built around the ferrocyanide as the active ingredient, such as to prevent oxidation of the ferrous ions in the active ingredient to ferric ions. Further, the compositions have been modified to include chelating agents which sequester heavy metal ions, such as ferric ions, which may be present either by virtue of any impurities or due to the hydrolysis of the ferrocyanide to the ferro-ferrous ions thereby preventing discoloration of the solutions.
Notwithstanding the various improvements that have been made in this art, conversion solutions will suffer from certain deficiencies, particularly under conditions of continued usage in a duplicator environment wherein a certain amount of evaporation occurs in the aqueous system. Understandably, such evaporation may be considerable, thereby concentrating the various ingredients to as much as twice their original level. This results in the formation of various salt crystals. Such salt crystals are the reaction product of the ferrocyanide with phosphoric acid which must be present to maintain an acidic pH. The precipitation of such crystals endangers the various fragile surfaces to which the conversion solution must be applied. Hence, it is critical that the formation of any such salt crystals be avoided to protect the photoconductive printing surfaces.